The Detroit Tigers released left-handed reliever Nate Robertson on Saturday.

Robertson, 36, was pitching for the team's Triple-A affiliate in Toledo. He had a 3.43 ERA but walked 13 batters in 21 innings in trying to work his way back to the major-league level.

Robertson was part of the Tigers' rotation from 2004-08 but has not pitched in the majors since 2010.